Insulating layer, semiconductor device and methods for fabricating the same

ABSTRACT

An insulating layer having a BPSG layer, a semiconductor device and methods for fabricating them. After preparing an oxidizing atmosphere using an oxygen gas, a first seed layer is formed with a tetraethylorthosilicate (TEOS) and the oxygen gas. Thereafter, a second seed layer, used to form an insulating layer capable of controlling an amount of a boron, is formed by means of using a triethylborate (TEB), the TEOS and the oxygen gas. Then, the insulating layer having a BPSG layer is formed using the TEB, a triethylphosphate, the TEOS and an ozone gas. About 5.25 to 5.75% by weight of the boron and about 2.75 to 4.25% by weight of the phosphorous are added to the insulating layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an insulating layer, a semiconductordevice and methods for fabricating the same, and more particularly, toan insulating layer, a semiconductor device and methods for fabricatingthe same that includes a borophosphosilicateglass (BPSG) layer tocontrol the additive amounts of boron (B) and phosphorous (P) mostefficiently.

2. Description of the Related Art

Semiconductor devices require high capacity and fast operating speeds topower today's electronic devices. Accordingly, semiconductor devicemanufacturing methods continually strive to improve the integrationdensity, reliability, and response times of the devices. As one example,consider the DRAM memory class, where 16M and 64M devices are being massproduced, 256M devices are starting to be mass produced, and plans formass production of 1G devices are being explored.

Critical techniques to improve the integration density of semiconductordevices include layer fabricating techniques for insulating andconductive layers. The layer fabricating techniques can largely beclassified into physical vapor deposition and chemical vapor deposition.The chemical vapor deposition technique provides a gas source, whichincludes supplying an element of an object material to be formed, and areaction gas onto a substrate, and then forms a layer on the substrateby heating the substrate to initiate a chemical reaction.

As the semiconductor devices become more advanced, the parameters andrequirements for the processing techniques to form a layer used forfabricating a semiconductor device are becoming more rigorous. This isbecause the insulating layers and conducting layers are formed in amulti-layer structure, and those layers have to be formed in a finepattern with a design rule of 0.15 μm or less.

When those layers are formed to have the fine patterns, the processcharacteristics for making the fine pattern affect not only the layer onwhich the fine pattern is formed, but also the underlying and upperlayers. Therefore, when the layers are formed, the chemical and physicalcharacteristics of the other layers must be considered when deciding onthe process characteristics of the layer to be formed.

A phosphosilicateglass (PSG) layer, which dopes phosphorus into anoxidized material, or a BPSG layer, which dopes boron and phosphorusinto an oxidized material, are the primary layer types used for aninsulating layer to protect a surface or to electrically isolate a metalwire. This is mainly due to the excellent step coverage of the PSG layeror the BPSG layer. Also, the PSG or BPSG layers getter alkali ion whilereacting as a diffusion wall against humidity, and the processes forforming the layers can easily be performed in a low temperature regime.

However, there is a disadvantage to using PSG or BPSG layers. Sincethese layers have enough fluidity and create a diffusion wall during areflow process, the layers also operate as an intermediary to pass onthe humidity to the underlying layers. Accordingly, in a case where alayer is composed of a material that can be damaged by humidity, or anunderlying substrate is made of silicon, it may cause a serious problem.Therefore, a method to minimize the influence of the humidity has to befully considered when the PSG and BPSG layers are being formed.

Examples for forming PSG and BPSG insulating layers are disclosed inU.S. Pat. No. 4,668,973 (issued to Dawson et al.), Japanese PatentLaid-Open No. Sho 59-22945, Japanese Patent Laid-Open No. Hei 1-122139,and Japanese patent Laid-Open No. Hei 8-17926.

In U.S. Pat. No. 4,668,973, the PSG layer is formed by adding 7% or lessof phosphorus into a nitride silicon layer after forming the nitridesilicon layer on the substrate. Accordingly, the nitride silicon layerprevents the humidity from penetrating into the substrate even thoughthe PSG layer has been reflowed. Furthermore, even if a window is formedat the PSG layer, since the substrate is not directly exposed by meansof the nitride silicon layer, the substrate may be prevented from beingoxidized.

In Japanese Patent Laid-Open No. Sho 59-222945, a nitride silicon layeris formed on a substrate and then a BPSG layer is formed on the nitridesilicon layer. The nitride silicon layer prevents the humidity frompenetrating into the substrate even though the BPSG layer has beenreflowed. Therefore, it is able to prevent the substrate from beingoxidizing by direct exposure.

In Japanese Patent Laid-Open No. Hei 1-122139, a nitride silicon layeris successively formed on the substrate and a gate electrode andthereafter a BPSG layer containing boron is formed. Therefore, thenitride silicon layer prevents the humidity from penetrating into thesubstrate or the gate electrode even though the BPSG layer has beenreflowed.

In Japanese Patent Laid-Open No. Hei 8-17926, an oxide silicon layer isformed onto a polysilicon layer and then the BPSG layer is formed ontothe oxide silicon layer. Therefore, the oxide silicon layer prevents thehumidity from penetrating into the polysilicon layer or the substrateeven if the BPSG layer has been reflowed.

In this way, when forming the insulating layer including the PSG layeror BPSG layer, the effect of the humidity can be minimized by means offorming the PSG layer or BPSG layer on the underlying nitride siliconlayer. Also, the nitride silicon layer prevents the underlying layer orthe substrate from being damaged by means of etching, for example, whena portion of the insulating layer is patterned and etched to form awindow.

In the present fabricating method for a semiconductor device havingelevated regions and recessed regions composed of minute windows or gateelectrodes, one must consider the need to sufficiently force or chargethe BPSG insulating layer into the recessed regions of the windows orthe gate electrodes. Therefore, a chemical vapor deposition using atetraethylorthosilicate (TEOS), a triethylborate (TEB), atriethylphosphate (TEPO), an oxygen gas and an ozone gas is employed toform the BPSG layer.

The BPSG layer is formed as follows. First, an oxidizing atmosphere foreasily forming the BPSG layer is prepared using oxygen gas. Afterforming a first seed layer onto an etch stop layer comprising thenitride silicon layer using the TEOS and the oxygen gas, a second seedlayer is formed onto the first seed layer using the triethylborate(TEB), the triethylphosphate (TEPO), the tetraethylorthosilicate (TEOS)and the oxygen gas. The constituents of the first and second seed layersdetermine the amount of boron and phosphorous added into the BPSG layer.Subsequently, the BPSG layer is formed onto the etch stop layerincluding the first and the second seed layers by using thetriethylborate, the triethylphosphate, the tetraethylorthosilicate andthe ozone gas. With this method, the BPSG layer is formed with arelatively large amount of phosphorous because the triethylphosphate isused to form the second seed layer.

While the BPSG layer has sufficient fluidity for normal circumstances,in a subsequent reflow process with nitrogen gas, the BPSG layer is notfully charged or filled into the recessed regions voids are frequentlygenerated.

Therefore, oxygen gas and hydrogen gas are sometimes used instead ofnitrogen gas to reflow the BPSG layer to minimize the generation ofvoids. However, when the BPSG layer has been reflowed with the oxygengas and the hydrogen gas, the thickness of the etch stop layer under theBPSG layer is decreased. This is because phosphoric acid H₃PO₄ isgenerated by a chemical reaction between the triethylphosphate, whichdetermines the amount of phosphorus, and the oxygen gas and the hydrogengas, which acid etches the etch stop layer while reflowing progresses.

Indeed, the thickness of the etch stop layer decreased by about 30%after reflowing with oxygen/hydrogen according to an analyzed result ofthe etch stop layer before and after the reflow with a transmissionelectron microscope (TEM). Also, using auger electron spectroscopy(AES), it was seen that the oxidized materials composing the etch stoplayer after reflowing have been increased about 0.2 times more thanbefore reflowing. This confirms that the thickness of the etch stoplayer is decreased by the reflowing process and the oxidization isprogressing thereby.

Given the above, the etch stop layer is unable to appropriately controlthe etching process when the BPSG layer is etched to form a BPSG layerpattern having a window after the reflowing. Consequently, the substrateunder the etch stop layer is exposed, or even the substrate itself isetched. In a semiconductor device fabricating process which requires afine pattern such as a self-aligned contact, the decrease in thicknessof the etch stop layer precludes attaining a sufficient shoulder marginbetween the gate electrodes.

Even when using a BPSG layer containing a relatively large amount of theboron, rather than the PSG layer containing a relatively large amount ofthe phosphorous, the BPSG layer is not charged into the recessed regionand voids are created because the BPSG layer does not have sufficientfluidity. Also, since the BPSG layer has an isotropic etchcharacteristic, the etched window that is formed is larger than apredetermined critical dimension CD. Therefore, in the subsequentprocess for charging the window, the inside portion of the window is notsufficiently charged and a void is generated. Accordingly, when thelayer for charging the window is made of a metal, the void may cause abridge.

As described above, since the amount of the phosphorous and the boronadded to the BPSG layer is not controlled, the thickness of theunderlying etch stop layer decreases or the etch stop layer has theisotropic etch characteristic, whereby the reliability of thesemiconductor device fabricating method is reduced.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide aninsulating layer including a BPSG layer capable of optimizing the amountof boron and phosphorous without a changing the characteristics of thelayer.

It is another object of the present invention to provide a method forforming an insulating layer including a BPSG layer capable of optimizingthe amount of the boron and phosphorous without changing thecharacteristics of the layer.

It is still another object of the present invention to provide asemiconductor device including an insulating layer constituted of a BPSGlayer capable of optimizing the amount of boron and phosphorous withoutchanging the characteristics of the layer.

To achieve the aforementioned object, the present invention includes aninsulating layer of a semiconductor device comprising a BPSG layer, inwhich about 5.25-5.75% by weight of boron and about 2.75-4.25% by weightof phosphorus are added to a tetraethylorthosilicate.

To achieve another object of the present invention, there is provided amethod for forming an insulating layer including steps of preparing anoxidizing atmosphere to form the insulating layer on a substrate byusing an oxygen gas, forming a first seed layer of the insulating layeron the substrate by using a tetraethylorthosilicate and an oxygen gas,forming a second seed layer of the insulating layer capable ofcontrolling an amount of a boron added to the first seed layer by usinga triethylborate, the tetraethylorthosilicate and the oxygen gas, andforming a BPSG layer capable of controlling the amount of the boron anda phosphorus added to the insulating layer having the first seed layerand second seed layer by using the triethylborate, triethylphosphate,the tetraethylorthosilicate and an ozone gas.

The insulating layer can be formed as follows. After preparing theoxidizing atmosphere, the first seed layer is formed by providing thetetraethylorthosilicate and the oxygen gas with a mixed ratio of 1:5.4to 5.8, and the second seed layer is formed by providing thetetraethylorthosilicate, the triethylborate and the oxygen gas with amixed ratio of 1:0.2 to 0.3:5.4 to 5.8. Next, the BPSG layer is formedonto the first seed layer and the second seed layer by providing thetetraethylorthosilicate, the triethylborate, the triethylphosphate andthe ozone gas with a mixed ratio of 1:0.2 to 0.3:0.09 to 0.12:5.4 to5.8. The insulating layer is formed under a reduced pressure (which isclose to a vacuum environment) in an atmosphere of helium gas and anitrogen gas with a mixed ratio of 1:1.8 to 2.2.

The etch stop layer on the substrate consists of a nitride silicon layerto prevent the substrate from being damaged by etching when theinsulating layer is etched. The insulating layer is reflowed withhydrogen and oxygen gas to evenly form the upper surface of theinsulating layer and simultaneously charge the recessed regions amongthe elevated regions and the recessed regions at the surface of thesubstrate.

Even though the insulating layer has been reflowed by the oxygen gas andthe hydrogen gas, the etch stop layer prevents the substrate from beingdamaged, so that an isotropic etch characteristic can be reduced. As aresult, the recessed regions can be fully charged and simultaneously theinsulating layer can be etched in an anisotropic etch. Accordingly, theinventive insulating layer having the BPSG layer can be appropriatelyadopted to form a self-aligned contact and a fine pattern.

To achieve still another object of the present invention, there isprovided a semiconductor device including a substrate having a gateelectrode formed at an upper portion of the substrate, a source and adrain formed at a lower portion of both sides of the gate electrode, andan insulating layer to which about 5.25-5.75% by weight of boron andabout 2.75-4.25% by weight of phosphorus is added, where the insulatinglayer is continuously formed on the substrate and the gate electrode.

To achieve yet another object of the present invention, there isprovided a method for fabricating a semiconductor device including thesteps of forming an etch stop layer on a substrate for preventing thesubstrate from being damaged by etching, forming an insulating layer, towhich about 5.25-5.75% by weight of boron and about 2.75-4.25% by weightof phosphorus is added, on the etch stop layer, reflowing the insulatinglayer to evenly form an upper surface of the insulating layer andsimultaneously charge recessed regions with the insulating layer amongelevated regions and recessed regions of the substrate, and etching apredetermined portion of the insulating layer to form an insulatinglayer pattern having a window which exposes the surface of theunderlying etch stop layer.

The substrate has elevated regions and recessed regions and the elevatedregions and the recessed regions are formed by the gate electrodes andthe patterns having the window.

The etch stop layer is formed to have a thickness of about 60 to 140 Åby using a nitride silicon gas and the insulating layer is formed tohave a thickness of about 9,000 to 10,000 Å. The etch stop layer and theinsulating layer are formed by means of a chemical vapor deposition.

Accordingly, the recessed regions can be sufficiently charged andsimultaneously the insulating layer can be etched by an anisotropicetch. By controlling the amount of added phosphorus and boron mostefficiently, the etch stop layer prevents the substrate from beingetched even though the insulating layer having the BPSG layer has beenreflowed and the isotropic etch characteristic is reduced. Therefore,the insulating layer having the BPSG layer can be appropriately adoptedfor the self-aligned contact which requires the design rule of 0.15 umor less or for forming fine patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and other advantages of the present invention willbecome more apparent by describing in detail with reference to theattached drawings, in which:

FIG. 1A to FIG. 1F are sectional views illustrating a method forfabricating an insulating layer according to a preferred embodiment ofthe present invention;

FIG. 2 is a cross-sectional view showing an apparatus for forming aninsulating layer according to a preferred embodiment of the presentinvention;

FIG. 3 is a schematic diagram describing a mixing process of thereaction gases shown in FIG. 2;

FIG. 4 is a graph classifying the materials used in a process to form aninsulating layer of the present invention in respective steps;

FIGS. 5 and 6 are graphs showing the thickness changes of an etch stoplayer by reflowing according to the added amount of a boron and aphosphorous; and

FIG. 7A to FIG. 7E are sectional views describing a method forfabricating a semiconductor device according to a preferred embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the present invention will now be described more fully withreference to the accompanying drawings, in which preferred embodimentsof the present invention are shown.

FIG. 1A to FIG. 1F are sectional views illustrating a method for formingan insulating layer according to a preferred embodiment of the presentinvention. Referring to FIG. 1A, an etch stop layer 12 is formed on asubstrate 10. The etch stop layer 12 is formed by chemical vapordeposition using a nitride silicon. Therefore, when an insulating layerformed on the substrate 10 is etched, the etch stop layer 12 preventsthe substrate 10 from being damaged by the etching and simultaneouslyprevents the substrate 10 from being oxidized by exposure to an oxygencontaining environment. Also, the etch stop layer 12 prevents anyhumidity generated while the insulating layer is reflowed frompenetrating into the substrate 10, since the insulating layer canoperate as an intermediary in delivering the humidity to adjacentlayers.

As described later, an insulating layer including a BPSG layer, to whichboron and phosphorous are added, is formed on the etch stop layer 12.The insulating layer is formed by chemical vapor deposition.

Jumping to FIG. 2, there is shown a cross-sectional view of an apparatusfor forming an insulating layer according to a preferred embodiment ofthe present invention. In FIG. 2, a stage 200 is equipped to accommodatea exemplary substrate 30 thereon. In the stage 200, heating elements forheating the substrate 30 are installed when the insulating layer isformed. Also, elevating elements for lifting the substrate 30 up anddown are arranged in the stage 200, and the substrate 30 is lifted upand down by the elevating elements when the insulating layer is formed.Since the lifting operation of the substrate 30 affects the uniformityof the insulating layer, the lifting operation intervals have to becontrolled at respective steps. Gas supplying lines 210 a and 210 b forsupplying reaction gases at each step, and a gas mixing box 220 formixing the reaction gases supplied through the gas supplying lines 210 aand 210 b, are equipped in a chamber 20 having the stage 200.

A plate 230 in the upper part of the chamber 20 uniformly provides thereaction gases supplied through the gas mixing box 220 onto thesubstrate 30 in the chamber 20. Along the surface of the plate, holesfor supplying gases are formed and the gases are uniformly supplied tothe substrate 30 through the holes.

FIG. 3 is a schematic diagram describing a mixing process of thereaction gases shown in FIG. 2. In FIG. 3, the gas mixing box 220 isconnected to the gas supplying lines 210 a and 210 b. The reaction gasesare supplied into the gas mixing box 220 and mixed in the gas mixing box220, and then supplied into the chamber 20.

Now, referring back to FIG. 1B, the insulating layer using the justdescribed apparatus including the chamber is formed as follows.

In FIG. 1B, when the substrate 10 having the etch stop layer 12 formedthereon is moved into the chamber 20, an oxygen gas is supplied into thechamber 20 at about 4,500 sccm to surround the substrate 10 in anoxidizing atmosphere 13 to maintain the uniformity of the insulatinglayer and this process continues for about 2 seconds. The pressureinside chamber 20 is reduced to be close to a vacuum condition, and ishereafter referred to generally as a vacuum environment, by utilizingpumping members connected to the chamber 20. The atmosphere is preparedwith a helium gas of about 2,000 sccm and a nitrogen gas of about 4,000sccm. Also, the stage 200 maintains the temperature at about 480° C.while heating the substrate, and the interval between the stage 200 andplate 230 is maintained at about 600 mils (note that 1 mil=25 μm).

In FIG. 1C, after preparing the oxidizing atmosphere 13, a first seedlayer 14 is formed on the etch stop layer 12 by using atetraethylorthosilicate (TEOS) and an oxygen gas. The TEOS and theoxygen gas are supplied at about 800 sccm and about 4,500 sccm,respectively. The oxygen gas, which was used previously to prepare theoxidizing atmosphere 13, is continuously supplied, and the TEOS issupplied thereafter. Then they are mixed in the gas mixing box 220 anduniformly supplied onto the substrate 10 through the plate 230 to formthe first seed layer 14. After preparing the oxidizing atmosphere, thefirst seed layer is formed by providing the tetraethylorthosilicate andthe oxygen gas with a mixed ratio of 1:5.4 to 5.8. Also, the chamber 20continuously maintains the vacuum environment. The stage 200 heats thesubstrate 10 while uniformly keeping the temperature at about 480° C.and the interval between the stage 200 and the plate 230 is kept atabout 400 mils. The formation process for the first seed layer 14continues for about 60 seconds.

In FIG. 1D, after forming the first seed layer 14, a second seed layer16 is formed on the first seed layer 14 by using a triethylborate (TEB),the TEOS and the oxygen gas. About 200 sccm of TEB, about 800 sccm ofTEOS, and about 4,500 sccm of the oxygen gas are supplied. The TEOS andthe oxygen gas for the previously formed first seed layer 14 arecontinuously supplied, and the TEB is supplied thereafter. They aremixed in the gas mixing box 220 and uniformly supplied onto thesubstrate 10 through the plate 230 to form the second seed layer 16. Thesecond seed layer is formed by providing the TEOS, the TEB and theoxygen gas with a mixed ratio of 1:0.2 to 0.3:5.4 to 5.8. The chamber 20continuously maintains a vacuum environment, the stage 200 heats thesubstrate 10 while uniformly keeping the temperature at about 480° C.,and the interval between the stage 200 and the plate 230 is kept atabout 310 mils. The process to form the second seed layer 16 iscontinuously executed for about 23 seconds.

The TEB is used as a source of a boron added to an insulating layer whenthe insulating layer having a BPSG layer is formed. The TEB is able tobe mixed with the TEOS without generating a residuum and is stable withrespect to heat.

In FIG. 1E, after forming the second seed layer 16, an insulating layer18 having the BPSG layer is formed on the etch stop layer 12 whichincludes the first seed layer 14 and the second seed layer 16 by usingthe TEB, the triethylphosphate (TEPO), the TEOS and ozone gas. About 200sccm of the TEB, about 85 sccm of the TEPO, about 800 sccm of the TEOS,and about 4,500 sccm of the ozone gas are supplied, respectively. TheTEOS and the TEB for the previously formed second seed layer 16 arecontinuously supplied, and the TEPO and the ozone gas are suppliedthereafter, with the oxygen gas being cut off. They are mixed in the gasmixing box 220 and uniformly supplied onto the substrate 10 through theplate 230 to form the insulating layer 18. The BPSG layer is formed ontothe first seed layer and the second seed layer by providing the TEOS,the TEB, the TEPO and the ozone gas with a mixed ratio of 1:0.2 to0.3:0.09 to 0.12:5.4 to 5.8. The chamber 20 is continuously maintainedin a vacuum environment, the stage 200 heats the substrate 10 whileuniformly keeping the temperature at about 480° C., and the intervalbetween the stage 200 and the plate 230 is kept at about 310 mils. Theprocess to form the insulating layer 18 is continuously executed forabout 160 seconds.

The TEPO is used as source of phosphorous added to the insulating layer18 when the insulating layer 18 having a BPSG layer is formed, and theTEPO is now more widely used rather than phosphine (PH₃).

FIG. 4 is a graph classifying and summarizing the materials used in theprocess to form an insulating layer of the present invention inrespective steps. In FIG. 4, the oxygen gas is supplied to prepare theoxidizing atmosphere and to form the first and the second seed layers;the TEOS is supplied to form the first seed layer, the second seed layerand the insulating layer; the TEB is supplied to form the second seedlayer and the insulating layer; and the TEPO and the ozone gas aresupplied to form the insulating layer.

As such, an insulating layer having a BPSG layer with about 5.5% byweight of the boron and about 3.0% by weight of the phosphorous isformed by controlling the triethylborate (TEB) provided as a sourcematerial of the boron and the triethylphosphate (TEPO) provided as asource material of the phosphorous. Accordingly, an insulating layerwhich has enough fluidity and simultaneously secures uniformity ofsurface can be formed.

Referring to FIG. 1F, the insulating layer 18 is reflowed at atemperature of about 850° C. utilizing oxygen gas and hydrogen gas.Consequently, the surface of the insulating layer 18 is evenly formedand simultaneously the recessed regions are charged with the insulatinglayer 18 among the elevated regions and the recessed regions of thesubstrate 10. Humidity is generated during the reflowing process, andthe insulating layer 18 acts as a diffusion wall against the humidityand getters alkali ion. However, the humidity does not penetrate intothe substrate 10 due to the etch stop layer 12.

Furthermore, the thickness of the etch stop layer 12 is not decreased bymore than 10 Å even if the insulating layer 18 is reflowed. This isbecause that the humidity reacts with the triethylphosphate (TEPO) addedas the source material of the phosphorous and minimizes the generationof the phosphoric acid.

An anisotropic etch characteristic can be sufficiently secured whenetching the insulating layer 18 to form an insulating layer patternhaving a window, while preventing the thickness of the etch stop layer12 from being decreased and at the same time, thoroughly charging therecessed regions. Accordingly, since the amount of the boron and thephosphorous added to the insulating layer 18 having the BPSG layer isappropriately controlled, the critical diameter of the window can beformed with a predetermined size.

By forming the insulating layer 18 having a BPSG layer with about 5.5%by weight of the boron and about 3.0% by weight of the phosphorous, thedecrease in thickness of the etch stop layer 12 by reflowing theinsulating layer 18 can be minimized, and the charging effect and theanisotropic etch characteristic can also be sufficiently secured.

The present inventors continued experimenting to determine the mostadvantageous amounts of boron and phosphorous that could be addedwithout changing the characteristics of the insulating layer having theBPSG layer.

FIGS. 5 and 6 are graphs showing the thickness changes of an etch stoplayer by reflowing with different added amounts of a boron and aphosphorous. Referring to FIG. 5, the graph represents the measureddecrease in thickness of the etch stop layer after reflowing the BPSGlayer to which about 5.5%, 6.0% and 6.5% by weight of the boron areadded, and in response to each amount of the boron, about 3.0%, 3.5% and4.0% by weight of the phosphorous are added thereto.

With reference to the line indicated by diamonds (⋄), in the case whereabout 3.0% by weight of the phosphorous and about 5.5% by weight of theboron are added to the BPSG layer, the thickness of the etch stop layerdecreases by about 10 Å. In the case where about 3.0% by weight of thephosphorous and about 6.0% by weight of the boron are added to the BPSGlayer, the thickness of the etch stop layer decreases by about 15 Å.Also, in the case where about 3.0% by weight of the phosphorous andabout 6.5% by weight of the boron are added to the BPSG layer, thethickness of the etch stop layer decreases by about 22 Å.

With reference to the line indicated by squares (□), in the case whereabout 3.5% by weight of the phosphorous and about 5.5% by weight of theboron are added to the BPSG layer, the thickness of the etch stop layerdecreases by about 15 Å. In the case where about 3.5% by weight of thephosphorous and about 6.0% by weight of the boron are added to the BPSGlayer, the thickness of the etch stop layer decreases by about 25 Å.Also, in the case where about 3.5% by weight of the phosphorous andabout 6.5% by weight of the boron are added to the BPSG layer, thethickness of the etch stop layer decreases by about 35 Å.

With reference to the line indicated by triangles (Δ), in the case whereabout 4.0% by weight of the phosphorous and about 5.5% by weight of theboron are added to the BPSG layer, the thickness of the etch stop layerdecreases by about 13 Å. In the case where about 4.0% by weight of thephosphorous and about 6.0% by weight of the boron are added to the BPSGlayer, the thickness of the etch stop layer decreases by about 35 Å.Also, in the case where about 4.0% by weight of the phosphorous andabout 6.5% by weight of the boron are added to the BPSG layer, thethickness of the etch stop layer decreases by about 45 Å.

Referring to FIG. 6, the graph represents a measured result of thedecrease in thickness of the etch stop layer after reflowing the BPSGlayer to which about 3.0%, 3.5% and 4.0% by weight of the phosphorousare added, and in response to each amount of the phosphorous, about3.0%, 3.5% and 4.0% by weight of the boron are added thereto.

With reference to the graph indicated by diamonds (⋄), in the case whereabout 3.0% by weight of the phosphorous and about 5.5% by weight of theboron are added to the BPSG layer, the thickness of the etch stop layerdecreases by about 8 Å. In the case where about 3.5% by weight of thephosphorous and about 5.5% by weight of the boron are added to the BPSGlayer, the thickness of the etch stop layer decreases by about 13 Å.Also, in the case where about 4.0% by weight of the phosphorous andabout 5.5% by weight of the boron are added to the BPSG layer, thethickness of the etch stop layer decreases by about 12 Å.

With reference to the graph indicated by squares (□), in the case whereabout 3.0% by weight of the phosphorous and about 6.0% by weight of theboron are added to the BPSG layer, the thickness of the etch stop layerdecreases by about 1 Å. In the case where about 3.5% by weight of thephosphorous and about 6.0% by weight of the boron are added to the BPSGlayer, the thickness of the etch stop layer decreases by about 25 Å.Also, in the case where about 4.0% by weight of the phosphorous andabout 6.0% by weight of the boron are added to the BPSG layer, thethickness of the etch stop layer decreases by about 35 Å.

With reference to the graph indicated by triangles (Δ), in the casewhere about 3.0% by weight of the phosphorous and about 6.5% by weightof the boron are added to the BPSG layer, the thickness of the etch stoplayer decreases by about 22 Å. In the case where about 3.5% by weight ofthe phosphorous and about 6.5% by weight of the boron are added to theBPSG layer, the thickness of the etch stop layer decreases by about 35Å. Also, in the case where about 4.0% by weight of the phosphorous andabout 6.5% by weight of the boron are added to the BPSG layer, thethickness of the etch stop layer decreases by about 45 Å.

According to FIG. 5 and FIG. 6, the thickness is hardly affected by theamount of phosphorous when about 5.5% by weight of the boron is added.Also, when the insulating layer is formed after setting about 5.5% byweight of the boron and 3.0% by weight of the phosphorous as the mostproper condition, the triethylphosphate (TEPO) supply which decides theamount of the phosphorous is controlled. Of course, it is understoodthat a range of values surrounding these optimal values would produce asufficient quality insulating layer. For example, about 5-6% by weightof boron, and about 2-5% by weight of phosphorus still produce a goodquality insulating layer, and preferably 5.25-5.75% by weight of boron,and about 2.75-4.25% by weight of phosphorus still produce a goodquality insulating layer.

Therefore, an insulating layer having a BPSG layer in which thethickness of the underlying etch stop layer decreases no more than 10 Åafter the reflowing, and simultaneously having a charging effect and ananisotropic etch characteristic can be formed. Thus, the insulatinglayer can be aggressively adopted to fabricate the semiconductor devicewhich requires a design rule of 0.15 um or less. That is, the insulatinglayer of the present invention can be adopted to form a self-alignedcontact and to form an inter-layer insulating layer, such as an intermetal dielectric (IMD), or an inter layer dielectric (ILD).

The example applying the inventive insulating layer for forming theself-aligned contact into the semiconductor device is described withrespect to FIG. 7A to FIG. 7E, which are sectional views describing amethod for fabricating a semiconductor device according to a preferredembodiment of the present invention.

Referring to FIG. 7A, gate electrodes 74 constituting transistors areformed on a substrate 70 on which a source and a drain 72 are formed.The source and the drain 72 are formed by means of injecting impuritiesinto the substrate 70, and the gate electrodes 74 are formed bydepositing a polysilicon layer and a tungsten silicon WSi layer, and byphotolithography etching the layers through a mask.

In FIG. 7B, an etch stop layer 76 comprising a nitride silicon layer issuccessively formed on the substrate 70 and the gate electrodes 74. Thenitride silicon layer is formed to have a thickness of about 80 Å bychemical vapor deposition. The nitride silicon layer prevents thesubstrate 70 from being damaged by etching and prevents the substrate 70from being oxidized by exposure, and simultaneously prevents thepenetrating of humidity generated by reflowing into the substrate 70.

In FIG. 7C, the insulating layer 78 having about 5.5% by weight of theboron and about 3.0% by weight of the phosphorous is formed on the etchstop layer 76. The insulating layer consists of a BPSG layer which isformed by adding to the TEOS, the triethylborate (TEB) used as thesource material of the boron and the triethylphosphate (TEPO) used asthe source material of phosphorous. The insulating layer 78 is formed tohave a thickness of about 9,500 Å.

To form the insulating layer 78 having the BPSG layer, an oxidizingatmosphere is prepared around the substrate 70 on which the etch stoplayer 76 is formed. About 4,500 sccm of the oxygen gas is supplied toprepare the oxidizing atmosphere. Then, about 4,500 sccm of the oxygengas and about 800 sccm of the TEOS are sequentially supplied thereto toform the first seed layer on the etch stop layer. Next, about 4,500 sccmof the oxygen gas, about 800 sccm of the TEOS, and about 200 sccm of thetriethylborate (TEB) used as the source material of boron, are suppliedthereto to form the second seed layer on the first seed layer.Thereafter, about 800 sccm of the TEOS, about 200 sccm of the TEB, about85 sccm of the triethylphosphate (TEPO) used as the source material ofphosphorous, and about 4,500 sccm of the ozone gas are supplied theretoto form the BPSG layer on the etch stop layer having the first and thesecond seed layers.

The BPSG layer is formed in a vacuum environment, and the vacuumenvironment is prepared by supplying about 2,000 sccm of the helium gasand about 4,000 sccm of the nitrogen gas. The temperature of the stagewhich supports the substrate maintains about 480° C.

In FIG. 7D, the insulating layer 78 is reflowed at a temperature ofabout 850° C. using hydrogen gas and oxygen gas. Accordingly, thesurface of the insulating layer 78 is evenly formed and at the sametime, the insulating layer 78 is sufficiently charged between the gateelectrodes 74.

Since the insulating layer 78 is formed by the BPSG layer having about5.5% by weight of the boron and about 3.0% by weight of the phosphorus,the decrease in thickness of the nitride silicon layer 76 thereunder canbe reduced by less than 10 Å, and simultaneously enough charging effectcan be achieved.

In present semiconductor devices, since the gap between the elevatedregions and the recessed regions formed by the gate electrodes are veryclose, it is not easy to sufficiently charge the gaps among the gateelectrodes, unless the insulating layer has sufficient fluidity. Theelevated and recessed regions are not restricted to those made by justgate electrodes, but also the elevated and recessed regions formed bythe patterns like the window.

In FIG. 7E, the insulating layer 78 is formed as an insulating layerpattern 82 having the window 80 by executing the self-aligned contact.The window 80 is formed by photolithographic etching, and an etching gasincluding CFx (wherein x is a positive number) is used to etch theinsulating layer 78. The etching is executed with a selectivity ratio ofthe insulating layer 78 and the nitride silicon layer 76 thereunder.Also, the etch is easily stopped because the thickness of the nitridesilicon layer 76 is not changed by the reflowing. Moreover, the shouldermargin can be sufficiently secured when the self-aligned contact isimplemented by the nitride silicon layer 76. Accordingly, when the nextprocess for charging the window is executed with the metal layer, thewindow 80 can be sufficiently charged by the metal layer.

Accordingly, in the semiconductor device fabrication, the insulatinglayer having the BPSG layer which is not affected by the processingcharacteristic before and/or after can be formed by efficientlycontrolling the amount of the boron and the phosphorous in the layer.

The decrease in thickness of the etch stop layer thereunder can beminimized, and simultaneously, the sufficient charging effect and theanisotropic etch characteristic can be secured even if the insulatinglayer is reflowed using hydrogen gas and oxygen gas. Thus, when theinsulating layer is adopted to processes for fabricating thesemiconductor devices, it is expected to elevate the reliability of thesemiconductor device.

While the present invention has been particularly shown and describedwith reference to a particular embodiment thereof, it will be understoodby those skilled in the art that various changes in form and details maybe effected therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A method for forming an insulating layercomprising: preparing an oxidizing atmosphere by supplying oxygen gasinto a chamber to surround a substrate on which the insulating layerwill be formed; forming a first seed layer of said insulating layer onsaid substrate by supplying a tetraethylorthosilicate (TEOS) and theoxygen gas into the chamber; forming a second seed layer of saidinsulating layer, said second seed layer capable of controlling anamount of boron added to said first seed layer by supplyingtriethylborate (TEB), the TEOS and the oxygen gas into the chamber; andforming a BPSG layer as the insulating layer, which includes said firstseed layer and said second seed layer, said BPSG layer capable ofcontrolling the amount of the boron and phosphorus added thereto bysupplying the TEB, the TEOS, triethylphosphate (TEPO), and an ozone gasinto the chamber.
 2. The method as claimed in claim 1, furthercomprising: reflowing said insulating layer to evenly form an uppersurface of said insulating layer using a hydrogen gas and the oxygengas, and simultaneously charging recessed regions with said insulatinglayer among elevated regions and recessed regions of a surface of saidsubstrate.
 3. The method as claimed in claim 1, wherein said first seedlayer is formed by supplying the TEOS and the oxygen gas into thechamber with a mixed ratio of about 1:5.4 to 5.8.
 4. The method asclaimed in claim 1, wherein said second seed layer is formed bysupplying the TEOS, the TEB and the oxygen gas into the chamber with amixed ratio of about 1:0.2 to 0.3:5.4 to 5.8.
 5. The method as claimedin claim 1, wherein said BPSG layer is formed by supplying the TEOS, theTEB, the TEPO, and the ozone gas into the chamber with a mixed ratio ofabout 1:0.2 to 0.3:0.09 to 0.12:5.4 to 5.8.
 6. The method as claimed inclaim 1, wherein said oxidizing atmosphere, said first seed layer, saidsecond seed layer and said BPSG layer are formed in a vacuum environmentin the chamber, and wherein the vacuum environment is provided bysupplying a helium gas and a nitrogen gas into the chamber with a mixedratio of about 1:1.8 to 2.2.
 7. The method as claimed in claim 1,wherein said insulating layer is formed after forming an etch stop layeron said substrate to prevent said substrate from being damaged byetching when said insulating layer is etched to form an insulating layerpattern having a window on said substrate.
 8. A method for fabricating asemiconductor device comprising: forming an etch stop layer on asubstrate for preventing said substrate from being damaged by etching;forming an insulating layer, to which about 5.25-5.75% by weight ofboron and about 2.75-4.25% by weight of phosphorus is added, on saidetch stop layer; reflowing said insulating layer to evenly form an uppersurface of said insulating layer, and simultaneously charging recessedregions with said insulating layer among elevated regions and recessedregions of said substrate; and etching a predetermined portion of saidinsulating layer to form an insulating layer pattern having a windowwhich exposes an upper surface of said underlying etch stop layer;wherein said forming said insulating layer comprises: forming a firstseed layer on said substrate by supplying a tetraethylorthosilicate(TEOS) and the oxygen gas into a chamber with a mixed ratio of about1:5.4 to 5.8; forming a second seed layer on said first seed layer bysupplying the TEOS, a triethylborate (TEB) and the oxygen gas into thechamber with a mixed ratio of about 1:0.2 to 0.3:5.4 to 5.8; and forminga BPSG layer as the insulating layer, including said first seed layerand said second seed layer, by supplying the TEOS, the TEB, atriethylphosphate and an ozone gas into the chamber with a mixed ratioof about 1:0.2 to 0.3:0.09 to 0.12:5.4 to 5.8, wherein said oxidizingatmosphere, said first seed layer, said second seed layer and said BPSGlayer are formed in a vacuum environment, and wherein the vacuumenvironment is provided by supplying helium gas and a nitrogen gas witha mixed ratio of 1:1.8 to 2.2.
 9. The method as claimed in claim 8,wherein said etch stop layer is comprised of nitride silicon and has athickness within the range of from about 60 to about 140 Å.
 10. Themethod as claimed in claim 8, wherein said elevated regions and therecessed regions are formed by gate electrodes.
 11. The method asclaimed in claim 8, wherein said elevated regions and the recessedregions are formed by patterns having a window.
 12. The method asclaimed in claim 8, wherein said insulating layer is formed to have athickness within the range of about from 9,000 to 10,000 Å.
 13. Themethod as claimed in claim 8, wherein said insulating layer is etched byan etch gas having a CFx structure.